1. Field of the Invention
The present invention relates to a storage tank for petroleum products, particularly a storage tank having a floating roof which is adapted to move above the petroleum product (hydrocarbons} stored in the tank and to lie in close proximity to the upper surface of the petroleum product. More particularly, the present invention relates to a stainless steel roof drain hose which is connected to the center of the floating roof and which passes downwardly into the bottom of the tank and discharges water at an outlet at the bottom side of the tank.
2. Prior Art
It is well known to attach a hose at the lower center of the floating roof and to direct the hose downwardly to the bottom of the tank, generally forming a loop at the bottom and then proceeding out to a drain opening at the bottom of the tank. The drain hose must be resistant to the hydrocarbons which are stored in the tanks. Some of the prior art hoses are made from rubber or plastic and some are made from stainless steel; still others are compound hoses where one hose is inside of another hose, one of which hoses can be stainless steel and the other of which hoses can be plastic or rubber.
It is extremely important that the rainwater be drained from the floating roof. Otherwise, the weight of the rainwater on the roof could cause the roof to sink into the petroleum product. If this should occur, the retrieval of a sunken roof is extremely difficult and generally quite costly, not to mention that the tank will suffer some down time while the roof is moved to its proper position.
It is a worthwhile consideration that the drain hose be inexpensive, in which case there is a tendency for the drain hose to be somewhat light in weight. On the other hand, if the drain hose is too light it has a tendency to be buoyed up in the petroleum product above the bottom of the tank, thus interfering with the free discharge of the rain water through the hose. Some hoses, therefore, are provided with outer covers to serve as ballast.
The present invention relates to a drain hose that connects to the movable roof of a petroleum storage tank. The hose extends downwardly through the material stored in the tank and to a discharge at the lower portion of the tank. The hose is comprised of (a) an inner stainless steel tube (or hose) having a stainless steel over-braid and (b) a spirally wound outer tube (or hose) also of stainless steel. The inner hose is connected to flanges that have ferrules extending therefrom. The outer protective hose is captured in a free floating manner by the ferrules such that the outer hose is allowed to move along or slide over the inner hose without escaping the end ferrules. Because the outer hose is free to move in the manner described above, the composite hose may flex, bend, stretch or contract without any consequent damage to any part of the hose; hence the term xe2x80x9cmulti-flex.xe2x80x9d